As is well known to those skilled in the art, many automatic transmissions include manual valve assemblies capable of directing fluid flow between a fluid source and a fluid-actuating device in the transmission.
Currently, there exists an automatic transmission system having a cam controlled manual valve assembly. A thorough discussion of such a cam controlled manual valve assembly is contained in U.S. Pat. No. 4,916,961 ('961) issued on Apr. 17, 1990, to Holbrook et al. and entitled "Cam-Controlled Manual Valve In An Automatic Transmission," which is commonly owned by the assignee of the present application. This patent is hereby incorporated by reference.
With reference to FIG. 4b of the '961 patent, the manually actuated valve assembly includes a manual lever having a cam groove formed thereon for actuating the manual valve of the transmission. The manual lever is rotated in response to a manual input from the operator. A valve pin connected to the manual valve is disposed in camming relationship with the cam groove of the manual lever such that when the manual lever is rotated, the pin travels within the cam groove to move the manual valve to a predetermined operating mode position (PRNODDL). However, it should be appreciated that the rotational movement of the manual lever relative to the valve pin may not afford maximum protection against bind. Furthermore, the curvature of the cam groove increases the difficulty of maintaining manufacturing tolerances in the manual lever.
Recently, attempts have been made to incorporate the electronic sensing system with the manual lever. A thorough discussion of such a transmission sensing system is contained in U.S. Pat. No. 5,325,083 ('083) issued on Jun. 28, 1994 to Nassar et al. and entitled "Manual Valve Position Sensing System," which is commonly owned by the assignee of the present application. This patent is hereby incorporated by reference.
With reference to FIGS. 3 and 6 of the '083 patent, the sensing system includes a plate member that rotates in response to the shift lever and includes a cam surface at the edge with electrically conductive and non-conductive areas. An electrical sensor unit is mounted in the transmission in a position to communicate with the contact surface of the plate member. Four electrical contact pins engage the conductive and non-conductive areas on the plate member and generate a binary code having combinations thereof that represent each of the shift lever positions and transition areas. However, like the '961 patent, the technique employed in the '083 patent may not afford maximum protection against bind in the cam when the plate member rotates relative to the valve pin. Moreover, the curvature of the cam groove increases the difficulty of maintaining manufacturing tolerances in the plate member. Still further, it may be difficult to maintain manufacturing tolerances in the electrically conductive and non-conductive areas, relative to the cam groove. Variations in the placement of the conductive and non-conductive areas relative to the cam groove may lead to the transmission controller incorrectly detecting the position of the manual valve.
Accordingly, there exists a need in the relevant art to provide a valve assembly capable of accurately positioning the manual valve that overcomes the disadvantages of the prior art. Furthermore, there exists a need in the relevant art to provide a valve assembly capable of minimizing bind in the cam groove caused from rotational motion. Still further, there exists a need in the relevant art to provide a valve assembly capable of providing a plate member having conductive and non-conductive areas formed accurately relative to a cam groove to insure improved position detection by a transmission controller.